Note: Descriptions are shown in the official language in which they were submitted.
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FUEL COMPOSITIONS
The present invention relates to fuel compositions,
to processes for their preparation and to their use in
the operation of compression-ignition engines.
It is known to treat hydrocarbons by passing them
through filtering or adsorbing material such as Fuller's
Earth or charcoal, e.g. as disclosed in US-A-2090007,
US-A-2338142 or GB-A-614636.
GB-A-437023 discloses a process for refining cracked
hydrocarbons of substantially gasoline boiling range by
the treatment with a solid active adsorbent such as
Fuller's Earth, clay or other suitable adsorptive
catalysts, under conditions of elevated temperature and
superatmospheric pressure adequate to maintain said
hydrocarbons in substantially liquid phase, which
comprises first removing from said hydrocarbons
relatively unstable low boiling constituents, namely
dissolved gases, propane, part or all of the butanes and
their corresponding unsaturates, and reducing the vapour
pressure of said hydrocarbons by submitting them to a
stabilising fractionation and thereupon subjecting the
stabilised hydrocarbons, whilst still hot, to said
refining treatment.
US-A-3529944 discloses a method for clarifying and
stabilising hydrocarbon liquids which are subject to
oxidative deterioration, particularly jet fuels, which
includes adding to the fuel a material which accelerates
the oxidative deterioration of the fuel, such as a
polyphenyl substituted lower alkane or lower alkylene, an
alkanol ester of citric acid or acetoxy ethyl
monobutylether; passing the hydrocarbon liquid through a
solid, particulate, adsorbent media to remove
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microimpurities and the products of oxidative
deterioration; and thereafter adding additional amounts
of a stabilising material to stabilise the hydrocarbon
liquid against further oxidative deterioration. Suitable
adsorbent materials (column 5, lines 22 to 25) include
various types of natural or synthetic clays, either
treated or untreated, Fuller's Earth, attapulgite, silica
gel and adsorbent catalysts. In the examples, jet fuels
are treated by filtration through attapulgite clay.
In US-A-4225319, in order to suppress carburettor
deposit formation, adsorbent-treated cat cracked gasoline
is blended into a fuel composition for use in an internal
combustion engine. In column 2, lines 57 to 62, it is
stated that adsorbents which are useful "for treating the
cat cracked gasoline include many of the well known
adsorbents such as silica, alumina, silica-alumina,
charcoal, carbon black, magnesium silicate, aluminium
silicate, zeolites, clay, fuller's earth, magnesia, and
the like". In the examples, the adsorbent used is
silica-gel.
US-A-5951851 relates to a process for removing
elemental sulphur from fluids, particularly fuels such as
gasoline, jet fuel, diesel, kerosene and fuel additives
such as ethers. The process involves contacting the
sulphur contaminated fluid with layered double hydroxide
(or hydrotalcite) Mg2AlNO3;mH2O or Mg3AlNO3;mH2O, where m
is the number of waters of hydration. In Example 1, it
is shown that Attapulgus clay, molecular sieve 5 A,
silica gel, alumina, bayerite, tetraphenylphosphonium-
montmorillonite, Kao-EG.9.4 A, Kao-tetraethylene glycol,
A113 pillared montmorillonite, tetramethylammonium-
montmorillonite, palygorskite-PF1-s, Kaolinite KGa-l,
Kao-cellosolve and Iron (III) montmorillonite are
ineffective in removing elemental sulphur, whilst the
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hydrotalcites A12LiCl, Mg2AlNO3, Mg2FeNO3, Mg3FeNO3 and
Mg3AlNO3 are particularly effective in removing elemental
sulphur.
The New Encylopaedia Britannica, Macropaedia, Volume
4, 15th Edition, 1984, ISBN 0-85229-413-1, pages 700 to
706 classifies clay minerals on the basis of variations
of atomic structure and chemical composition into 9
groups, viz (1) allophane, (2) kaolinite, (3) halloysite,
(4) smectite, (5) illite, (6) chlorite, (7) vermiculite,
(8) sepiolite, attapulgite and palygorskite and (9) mixed
layer clay minerals.
Group (8), sepiolite, attapulgite and palygorskite,
are described as fibrous clay minerals, and these have,
as an important structural element, the amphibole double
silica chain which is orientated parallel to the c axis.
It is known that diesel fuels can contain a number
of trace metals. The content of such metals depends on a
number of factors, including the source(s) of crude oil
from which the fuel is derived, the types of refinery
processes employed, and the handling, storage and
distribution history of the fuel.
It has now surprisingly been found that when at
least one hydrocarbon component of a diesel fuel
composition has been treated with a metal adsorbing or
absorbing material in a different physical phase from the
hydrocarbon component(s), which material may for example
be in liquid form which is immiscible (including having
minimal or low solubility) with the hydrocarbon
component, or a solid, preferably a solid, to reduce the
levels of trace metal contaminants, more preferably the
levels of heavier metals, most preferably the level of
zinc, in said component(s), the fuel composition exhibits
reduced levels of emissions, particularly of NOx, and
optionally particulates, when used in a
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compression-ignition engine to power such an engine.
Said treatment includes physical separation of the
hydrocarbon component from the metal adsorbing or
absorbing phase, for example by one or more of decanting
of immiscible liquid, filtration, vortexing, centrifuging
and gravity separation.
For the purpose of this disclosure, "heavier metals"
are defined as metals with atomic numbers of 20 or
greater.
In accordance with the present invention there is
provided a fuel composition comprising a major amount of
a fuel suitable for use in a compression-ignition engine,
which fuel comprises one or more hydrocarbon components
boiling within the diesel boiling range, at least one of
which hydrocarbon components has been treated with a
metal adsorbing or absorbing material in a different
physical phase from the hydrocarbon component(s),
preferably to reduce the level of at least one metal,
more preferably the level of at least one heavier metal,
most preferably the level of zinc, in said at least one
hydrocarbon component, for the purpose of reducing the
emission of NOx, and optionally particulates, from a
compression-ignition engine into the combustion chambers
of which said fuel composition is introduced, said
treatment including physical separation of the
hydrocarbon component from the metal adsorbing or
absorbing phase.
Preferably, the metal adsorbing or absorbing
material is selected from fibrous clay minerals,
diatomaceous earths, graphite, charcoal, polymeric
adsorbents or absorbents, ion-exchange resins, and
complexing or chelating agents, which materials may be in
liquid form which is immiscible (including having minimal
or low solubility) with the hydrocarbon component, or
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solids, more preferably solids. Said complexing or
chelating agents preferably comprise molecules having one
or more functional groups acting as a ligand or forming a
complex or being otherwise metal-attracting.
The fibrous clay mineral of the sepiolite,
attapulgite and palygorskite group must at least contain
at least one mineral of the sepiolite, attapulgite and
palygorskite groups. The term "Fuller's Earth" is used
in published literature on clays in a number of different
ways, but in the context of the present invention
"Fuller's Earth" comprises at least one fibrous clay
mineral of the sepiolite, attapulgite and palygorskite
groups. One type of Fuller's Earth may comprise a
mixture of montmorillonite and palygorskite.
Preferably the fibrous clay mineral is sepiolite,
attapulgite, or Fuller's Earth.
Preferably, said polymeric material is selected from
polyolefins such as polyacrylate or polystyrene,
polyester, polyether, polyamide, polyamine and
polysulphone materials, for example AMBERLITE XAD-4,
AMBERLITE XAD-7 and AMBERLITE XAD-16 non-ionic polymeric
adsorbents and polyethylene imine on silica gel
(available ex. Aldrich), said polymeric materials being
in solid form, or bound to a solid, or in liquid or
suspension or dissolved form which is immiscible
(including having minimal or low miscibility) with the
hydrocarbon component.
Preferably, examples of said diatomaceous earths are
DAMOLIN MOLER (available ex. Damolin) and HYFLO SUPER CEL
(available ex. Aldrich).
Preferably, said complexing or chelating agents are
selected from nitrogen materials such as amines, amides,
polyamines, cyclic polyamines including but not limited
to porphyrins, derivatives of N,N'-disalicylidene-
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propanediamine, sulphur materials such as sulphides,
sulphones, sulphoxides, sulphonates, thiols, anionic
materials such as carboxylates, oxygen species such as
alcohols, ketones, phenols and ethers, including
polyethers and cyclic polyethers (crown ethers), and
species containing both nitrogen and oxygen such as
cryptands and oxazoles and derivatives thereof, said
complexing or chelating agents being in solid form, or
bound to a solid, or in liquid or suspension or dissolved
form which is immiscible (including having minimal or low
miscibility) with the hydrocarbon component.
Preferably, said ion-exchange resins are selected
from mineral species, such as silica gels, and polymers
with functional groups such as sulphonate and carboxylate
such as some of the products available from Aldrich under
the trade names AMBERLITE, AMBERLYST, DOWEX and SEPHADEX.
Preferably, a blend of at least two of said
hydrocarbon components has been treated with the metal
adsorbing or absorbing material.
In accordance with the present invention there is
also provided a process for the preparation of a fuel
composition according to the present invention which
comprises treating with a metal adsorbing or absorbing
material at least one hydrocarbon component boiling
within the diesel boiling range, preferably to reduce the
level of at least one metal, more preferably the level of
at least one heavier metal, most preferably the level of
zinc, in said at least one hydrocarbon component, and
optionally blending said at least one hydrocarbon
component, before or after said treatment, with at least
one other hydrocarbon component boiling within the diesel
boiling range, to form a fuel suitable for use in a
compression-ignition engine.
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Preferably, said process comprises blending at least
two hydrocarbon components boiling within the diesel
boiling range and treating the resulting mixture with
said metal adsorbing or absorbing material, to form a
fuel suitable for use in a compression-ignition engine.
In accordance with the present invention there is
further provided a method of operating a
compression-ignition engine, which comprises bringing
into the combustion chambers of such engine a fuel
composition according to the present invention.
In accordance with the present invention there is
still further provided a method of reducing the emission
of NOx, and optionally particulates, from a compression-
ignition engine which comprises bringing into the
combustion chambers of such engine a fuel composition
according to the present invention.
In accordance with the present invention there is
still further provided the use in a compression-ignition
engine of a fuel composition according to the present
invention for the purpose of reducing the emission of
NOx, and optionally particulates, from said engine.
In accordance with the present invention there is
still further provided a method of reducing the emission
of NOx, and optionally particulates, from a compression-
ignition engine which comprises replacing a fuel
composition therein by a fuel composition according to
the present invention.
In this specification, the terms "reduce",
"reducing" and "reduction" mean as compared to prior to
the treatment with the metal adsorbing or absorbing
material or as compared to when using a diesel fuel
composition components of which have not been subjected
to said treatment, as appropriate.
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The processes of adsorption or absorption of trace
elements on to clay are not completely understood. One
possibility is that the metals bond to the surface in the
same way that they bond to ligands. Ligands are
molecules or ions that function as electron donors and
attract metal atoms or ions.
The fuel compositions to which the present invention
relates include diesel fuel compositions for use in
automotive compression ignition engines, as well as in
other types of engine such as for example marine,
railroad and stationary engines, and industrial gas oils
for use in heating applications (e.g. boilers), provided
that these non-automotive fuels do not contain residual
(non-distilled) components.
The base fuel may itself comprise a mixture of two
or more different diesel fuel components, and/or be
additivated as described below.
Such diesel fuel compositions will contain one or
more base fuels which may typically comprise liquid
hydrocarbon middle distillate gas oil(s), for instance
petroleum derived gas oils. Such fuel compositions will
typically have boiling points within the usual diesel
range of 150 to 400 C, depending on grade and use. They
will typically have a density from 750 to 1000 kg/m3,
preferably for automotive uses from 780 to 860 kg/m3, at
15 C (e.g. ASTM D4502 or IP 365) and a cetane number
(ASTM D613) of from 35 to 120, more preferably from 40 to
85. They will typically have an initial boiling point in
the range 150 to 230 C and a final boiling point in the
range 290 to 400 C. Their kinematic viscosity at 40 C
(ASTM D445) might suitably be from 1.5 to 6 mm2/s.
Such industrial gas oils will contain a base fuel
which may comprise fuel fractions such as the kerosene or
gas oil fractions obtained in traditional refinery
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processes, which upgrade crude petroleum feedstock to
useful products. Preferably such fractions contain
components having carbon numbers in the range 5 to 40,
more preferably 5 to 31, yet more preferably 6 to 25,
most preferably 9 to 25, and such fractions have a
density at 15 C of 650 to 1000 kg/m3, a kinematic
viscosity at 20 C of 1 to 80 mm2/s, and a boiling range
of 150 to 400 C.
Optionally, non-mineral oil based fuels, such as
Fischer-Tropsch derived fuels, biomass-derived materials,
biofuel components such as fatty acid methyl esters, or
shale oils, may also form or be present in the fuel
composition. Such Fischer-Tropsch fuels may for example
be derived from natural gas, natural gas liquids,
petroleum or shale oil, petroleum or shale oil processing
residues, coal or biomass.
The amount of Fischer-Tropsch derived fuel used in a
diesel fuel composition may be from 0.5 to 100%v of the
overall diesel fuel composition, preferably from 5 to
75%v. It may be desirable for the composition to contain
10%v or greater, more preferably 20%v or greater, still
more preferably 30%v or greater, of the Fischer-Tropsch
derived fuel. It is particularly preferred for the
composition to contain 30 to 75%v, and particularly 30 or
70%v, of the Fischer-Tropsch derived fuel. The balance
of the fuel composition is made up of one or more other
fuels.
An industrial gas oil composition will preferably
comprise more than 50 wt%, more preferably more than
70 wt%, of a Fischer-Tropsch derived fuel component.
Such a Fischer-Tropsch derived fuel component is any
fraction of the middle distillate fuel range, which can
be isolated from the (hydrocracked) Fischer-Tropsch
synthesis product. Typical fractions will boil in the
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naphtha, kerosene or gas oil range. Preferably, a
Fischer-Tropsch product boiling in the kerosene or gas
oil range is used because these products are easier to
handle in for example domestic environments. Such
products will suitably comprise a fraction larger than
90 wt% which boils between 160 and 400 C, preferably to
about 370 C. Examples of Fischer-Tropsch derived
kerosene and gas oils are described in EP-A-0583836,
WO-A-97/14768, WO-A-97/14769, WO-A-00/11116,
WO-A-00/11117, WO-A-01/83406, WO-A-01/83648,
WO-A-01/83647, WO-A-01/83641, WO-A-00/20535,
WO-A-00/20534, EP-A-1101813, US-A-5766274, US-A-5378348,
US-A-5888376 and US-A-6204426.
The Fischer-Tropsch product will suitably contain
more than 80 wt% and more suitably more than 95 wt% iso
and normal paraffins and less than 1 wt% aromatics, the
balance being naphthenics compounds. The content of
sulphur and nitrogen will be very low and normally below
the detection limits for such compounds. For this reason
the sulphur content of a fuel composition containing a
Fischer-Tropsch product may be very low.
The fuel composition preferably contains no more
than 5000 ppmw sulphur, more preferably no more than
500 ppmw, or no more than 350 ppmw, or no more than
150 ppmw, or no more than 100 ppmw, or no more than
50 ppmw, or most preferably no more than 10 ppmw sulphur.
The base fuel may itself be additivated (additive-
containing) or unadditivated (additive-free). If
additivated, e.g. at the refinery, it will contain minor
amounts of one or more additives selected for example
from anti-static agents, pipeline drag reducers, flow
improvers (e.g. ethylene/vinyl acetate copolymers or
acrylate/maleic anhydride copolymers), lubricity
additives, antioxidants and wax anti-settling agents.
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Detergent-containing diesel fuel additives are known
and commercially available. Such additives may be added
to diesel fuels at levels intended to reduce, remove, or
slow the build up of engine deposits.
Examples of detergents suitable for use in fuel
additives for the present purpose include polyolefin
substituted succinimides or succinamides of polyamines,
for instance polyisobutylene succinimides or
polyisobutylene amine succinamides, aliphatic amines,
Mannich bases or amines and polyolefin (e.g.
polyisobutylene) maleic anhydrides. Succinimide
dispersant additives are described for example in
GB-A-960493, EP-A-0147240, EP-A-0482253, EP-A-0613938,
EP-A-0557516 and WO-A-98/42808. Particularly preferred
are polyolefin substituted succinimides such as
polyisobutylene succinimides.
The additive may contain other components in
addition to the detergent. Examples are lubricity
enhancers; dehazer compositions, e.g. those containing
alkoxylated phenol formaldehyde polymers; anti-foaming
agents (e.g. polyether-modified polysiloxanes); ignition
improvers (cetane improvers) (e.g. 2-ethylhexyl nitrate
(EHN), cyclohexyl nitrate, di-tert-butyl peroxide and
those disclosed in US-A-4208190 at column 2, line 27 to
column 3, line 21); anti-rust agents (e.g. a propane-1,2-
diol semi-ester of tetrapropenyl succinic acid, or
polyhydric alcohol esters of a succinic acid derivative,
the succinic acid derivative having on at least one of
its alpha-carbon atoms an unsubstituted or substituted
aliphatic hydrocarbon group containing from 20 to 500
carbon atoms, e.g. the pentaerythritol diester of
polyisobutylene-substituted succinic acid); corrosion
inhibitors; reodorants; anti-wear additives; anti-
oxidants (e.g. phenolics such as 2,6-di-tert-butylphenol,
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or phenylenediamines such as
N,N'-di-sec-butyl-p-phenylenediamine); metal
deactivators; and combustion improvers.
It is particularly preferred that the additive
include a lubricity enhancer, especially when the fuel
composition has a low (e.g. 500 ppmw or less) sulphur
content. In the additivated fuel composition, the
lubricity enhancer is conveniently present at a
concentration of less than 1000 ppmw, preferably between
5 and 1000 ppmw. Suitable commercially available
lubricity enhancers include ester- and acid-based
additives. Other lubricity enhancers are described in
the patent literature, in particular in connection with
their use in low sulphur content diesel fuels, for
example in:
- the paper by Danping Wei and H.A. Spikes, "The
Lubricity of Diesel Fue1s", Wear, III (1986) 217-235;
- WO-A-95/33805 - cold flow improvers to enhance
lubricity of low sulphur fuels;
- WO-A-94/17160 - certain esters of a carboxylic
acid and an alcohol wherein the acid has from 2 to 50
carbon atoms and the alcohol has 1 or more carbon atoms,
particularly glycerol monooleate and di-isodecyl adipate,
as fuel additives for wear reduction in a diesel engine
injection system;
- US-A-5490864 - certain dithiophosphoric diester-
dialcohols as anti-wear lubricity additives for low
sulphur diesel fuels; and
- WO-A-98/01516 - certain alkyl aromatic compounds
having at least one carboxyl group attached to their
aromatic nuclei, to confer anti-wear lubricity effects
particularly in low sulphur diesel fuels.
It is also preferred that the additive contain an
anti-foaming agent, more preferably in combination with
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an anti-rust agent and/or a corrosion inhibitor and/or a
lubricity additive.
Unless otherwise stated, the (active matter)
concentration of each such additional component in the
additivated fuel composition is preferably up to
10000 ppmw, more preferably in the range from 0.1 to 1000
ppmw, advantageously from 0.1 to 300 ppmw, such as from
0.1 to 150 ppmw. The (active matter) concentration of
any dehazer in the fuel composition will preferably be in
the range from 0.1 to 20 ppmw, more preferably from 1 to
ppmw, still more preferably from 1 to 10 ppmw,
advantageously from 1 to 5 ppmw. The (active matter)
concentration of any ignition improver present will
preferably be 2600 ppmw or less, more preferably 2000
15 ppmw or less, conveniently from 300 to 1500 ppmw.
If desired, the additive components, as listed
above, may be co-mixed, preferably together with suitable
diluent(s), in an additive concentrate, and the additive
concentrate may be dispersed into the fuel, in suitable
quantity to result in a composition of the present
invention.
In the case of a diesel fuel composition, for
example, the additive will typically contain a detergent,
optionally together with other components as described
above, and a diesel fuel-compatible diluent, which may be
a carrier oil (e.g. a mineral oil), a polyether, which
may be capped or uncapped, a non-polar solvent such as
toluene, xylene, white spirits and those sold by Shell
companies under the trade mark "SHELLSOL".
The total content of the additives may be suitably
between 0 and 10000 ppmw and preferably below 5000 ppmw.
In this specification, amounts (concentrations, %v,
ppmw, wt%) of components are of active matter, i.e.
exclusive of volatile solvents/diluent materials.
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The treatment according to the present invention may
be applied before or after any additives are blended into
the fuel composition, as appropriate.
The present invention is particularly applicable
where the fuel composition is used or intended to be used
in a direct injection diesel engine, for example of the
rotary pump, in-line pump, unit pump, electronic unit
injector or common rail type, in an indirect injection
diesel engine or in a homogeneous charge compression
ignition engine. The fuel composition may be suitable
for use in heavy and/or light duty diesel engines.
As mentioned above, it is also applicable where the
fuel composition is used in heating applications, for
example boilers. Such boilers include standard boilers,
low temperature boilers and condensing boilers, and are
typically used for heating water for commercial or
domestic applications such as space heating and water
heating.
In the diesel fuel composition, hydrocarbons can be
supplemented by oxygenates such as esters known for use
in diesel fuel.
In the process of the present invention the
treatment with the metal adsorbing or absorbing material
is effected with the hydrocarbons in the liquid phase,
very conveniently at ambient temperature. At ambient
temperature, the treatment may very conveniently be
effected at atmospheric pressure.
Whilst when it is known that a particular
hydrocarbon refinery component or combination/components
of a fuel composition is at least predominantly
responsible for the presence of metals to be removed,
that component or combination of components may be
treated with the metal adsorbing or absorbing material
before blending with at least the other hydrocarbon
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refinery component to form the fuel composition, the
fully pre-blended fuel composition may also be treated.
The present invention will now be further described
by reference to the following Examples, in which, unless
otherwise indicated, parts and percentages are by weight,
and temperatures are in degrees Celsius:
EXAMPLES
Example 1
The fuels referred to in Example 1 were as set out
in Table 1:
Table 1
Property Fuel A Fuel B
Density @ 15 C 835.7 835.5
(kg/m3)
Cetane 52.7 53.3
Sulphur mg/kg 212 210
Distillation
( C)
IBP 183.0 185.3
10% rec 208.5 210.5
20% rec 221.5 222.8
30% rec 235.0 235.5
40% rec 248.5 249.1
50% rec 263.0 263.6
60% rec 277.5 278.2
70% rec 293.5 293.9
80% rec 311.5 310.6
90% rec 333.0 331.9
95% rec 350.0 348.3
FBP 361.0 361.1
HPLC aromatics
(%m/m)
Mono 26.8 26.7
Di 4.5 4.2
Tri 0.7 0.5
Total 32 31.4
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Fuel A was a market fuel from Hungary that is
compliant with EN590 and which was used without any
further treatment. Fuel B was Fuel A which had been
treated by being passed through a clay column as
described below.
By comparing the characteristics of Fuels A and B
set out in Table 1 it can be seen that the physical
properties (density and cetane number) were essentially
unchanged by the clay treatment. It can also be seen
that the aromatic (mono-, di- and tri-) content and
sulphur content were also essentially unchanged by said
treatment, as were the distillation characteristics.
Metals content and filtration
The metal content of Fuel A was determined using the
following technique, ICP-MS (Inductively Coupled
Plasma-Mass Spectrometry). Said technique involves
spraying the fuel containing the metals into a spray
chamber to form a fine spray. Here the larger droplets
are removed and 1 to 2% of the sample solution enters
into the inductively coupled plasma. The plasma is
produced in a quartz torch, via the interaction of an
intense magnetic field and flowing argon. The plasma
discharge has a high temperature, approximately 10000 C.
In ICP-MS the plasma is used to generate positively
charged ions. Once the ions are produced in the plasma,
they are directed into the mass spectrometer via the
interface region from where the positive ions are focused
down a quadruple mass spectrometer. The results (in
ppbw) are set out in Table 2 below.
A glass column of about 1 metre in height and
diameter of 7.5 cm, having a tap at the bottom and a
loose glass cap on top, was fitted with a glass wool
layer immediately above the tap and was then loaded with
0.5 kg of dry clay, in powder form. The clay filled the
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column to about 40 cm above the tap, and the glass wool
layer prevented clay from falling into the tap.
Fuel A at ambient temperature (20 C) was then poured
into the column, to a depth of 25 to 30 cm above the
clay. Flow rate was adjusted to 1 litre/hour, and the
column was regularly topped up with fuel. A total volume
of 50 litres was passed through the column. The first
litre of permeate was discarded, and subsequently 5 litre
samples (Fuel B) were collected. The 2nd, 4th, 6th, 8th
and final samples (Fuel B) were tested for metal content.
The average values (in ppbw) were as set out in Table 2
below:
Table 2
Metal Fuel A Fuel B
Ag <50 <50
B <50 <50
Cr 14 <5
Cu <50 <50
Fe 84 <5
Mg 76 <5
Mn 8 <5
Mo <50 <50
Ni <50 <50
Pb 50 <40
Sn <50 <50
Ti <50 <50
Zn 1500 26
V <50 <50
It is to be noted that the levels of chromium (Cr),
iron (Fe), lead (Pb), magnesium (Mg), manganese (Mn) and
zinc (Zn) were all reduced after the clay treatment. The
reduction in the level of zinc was particularly marked.
The levels of metals could be further reduced by the
optimisation of the operating conditions of the process,
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passing the fuel through a second bed of solid, or by
other means.
The clay which was employed was Attapulgite, mesh
size 30-60 (0.500 to 0.250 mm), ex. Wilfrid Smith Limited
(manufactured by Millwhite). Other suitable clays
include Fuller's Earth, e.g. mesh size 30-60, ex.
Aldrich, and Sepiolite, e.g. grade 30-60, ex. Steetly
Bentonite & Absorbents Ltd.
Emissions behaviour
The emissions behaviour of Fuels A and B was then
measured using the vehicles listed in Table 3, which
represent two major light duty fuel injection systems
(direct injection (DI) and indirect injection (IDI)):
Table 3
Vehicle Engine No. of No. of Injection
size (L) cylinders valves system
VW Golf 1.9 4 8 DI
VW Passat 1.9 4 8 IDI
Fuels A and B were tested in the above vehicles in
the sequence set out in Table 4:
Table 4
Vehicle Test fuel
VW Golf A A B B A A B B
VW Passat A A B B A A B B
Each test comprised a standard ECE + EUDC cycle (ECE
1505M lls 221) in which total hydrocarbons, NOx, C0, CO2
and particulates were measured using a 2 + 2 + 1 bagging
strategy.
Two vehicles were tested on one fuel during each
days testing:
Day 1: pre-condition both vehicles on Fuel A;
Day 2: emission test VW Golf and VW Passat on Fuel
A;
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Day 3: emission test VW Golf and VW Passat on Fuel
A, change fuel and pre-condition both
vehicles with Fuel B;
Day 4: emission test VW Golf and VW Passat on Fuel
B;
etc.
In order to avoid trace metal contamination of the
clay treated fuel, testing was conducted from
lacquer-lined fuel cans and non-metallic fuel lines to
each vehicle's fuel pump. Samples of fuels were retained
at the end of each emissions test and submitted for
elemental analysis. This confirmed that trace metal
contamination had not occurred during the course of
testing.
The results of the emissions testing are set out
below, namely in Table 5 (NOx), Table 6 (particulates),
Table 7 (CO), Table 8 (total hydrocarbons) and Table 9
(C02), the units in all said Tables being g/km:
Table 5
Fuel A Fuel B
W Golf 0.4236 0.3848
1W Passat 1.1849 1.1306
Fleet average 0.8043 0.7577
Table 6
Fuel A Fuel B
VW Golf 0.05665 0.05102
1W Passat 0.03843 0.03246
Fleet average 0.04754 0.04174
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Table 7
Fuel A Fuel B
7W Golf 0.577 0.572
VW Passat 0.245 0.249
Fleet average 0.411 0.411
Table 8
Fuel A Fuel B
7W Golf 0.137 0.138
1W Passat 0.019 0.018
Fleet average 0.078 0.078
Table 9
Fuel A Fuel B
IVW Golf 133.75 127.65
IVW Passat 176.20 174.51
Fleet average 154.98 151.08
It can be seen from Tables 7, 8 and 9 that the
levels of C0, total hydrocarbons and C02 were unchanged
or essentially unchanged as between Fuels A and B. The
benefits, i.e. percentage improvement, in levels of NOx
and particulates using Fuel B as compared to using Fuel A
are set out below, namely in Table 10 (NOx) and Table 11
(particulates):
Table 10
NOx benefit [ o ]
IVW Golf 9.2
VW Passat 4.6
Fleet average 6.9
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Table 11
Particulate
benefit [%]
W Golf 9.9
W Passat 15.5
Fleet average 12.7
Example 2
The fuels referred to in Example 2 were as set out
in Table 12:
Table 12
Property Fuel C Fuel D Fuel E Fuel F Fuel G
Density @ 15 C 0.8394 0.8391 0.8391 0.8394 0.8395
(g/cm3)
Fuel C was a 275ppmw sulphur diesel fuel. Fuels D,
E, F, and G were Fuel C which had been treated by being
passed through DAMOLIN MOLER (diatomaceous earth ex.
Damolin), AMBERLITE XAD-7 (polymeric adsorbent ex.
Aldrich), polyethylene imine on silica gel (ex. Aldrich),
and AMBERLYST 15 (ion-exchange resin, ex. Aldrich),
respectively, as described below.
It can be seen that the density of Fuels C to G was
essentially unchanged by the treatment.
Metals content and filtration
The metals content of Fuel C was determined using
the technique described in Example 1 with respect to Fuel
A. The results (in ppbw) are set out in Table 13 below.
Fuel C was then treated at ambient temperature
(20 C) with the metal adsorbing or absorbing materials
DAMOLIN MOLER, AMBERLITE XAD-7, polyethylene imine on
silica gel, and AMBERLYST 15, to produce Fuels D to G
respectively, as described below.
Fuel D was obtained when Fuel C was treated in a
column approximately lm high with a diameter of about
7.5cm and a tap at the bottom. Approximately 250g of dry
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solid was loaded into the column, on top of a layer of
glass wool. The solid filled the column to approximately
20cm above the tap. The fuel was passed once through the
column with the first -100ml being discarded.
Fuels E, F, and G were obtained when Fuel C was
treated in columns about 50cm high with a diameter of 2cm
and a tap at the bottom. In each case, approximately 40g
of solid was loaded into the column, on top of a layer of
glass wool. The solid filled the column to approximately
30cm above the tap. The fuels were passed once through
the columns, with the first -100ml being discarded.
Fuels D to G were then tested for metals content.
The average values (in ppbw) were as set out in Table 13
below:
Table 13
Metal Fuel C Fuel D Fuel E Fuel F Fuel G
Ag <20 <20 <20 <20 <20
Al <100 <100 <100 <100 Nd
B <500 <500 <500 <500 Nd
Cr <20 <20 <20 <20 <5
Cu 275 <10 30 145 130
Fe 10 <5 <5 <5 <5
Mg <100 <100 <100 <100 <5
Mn <5 <5 <5 <5 <5
Mo <20 <20 <20 <20 <20
Ni <20 <20 <20 <20 Nd
Pb <100 <100 <100 <100 <50
Sn <50 <50 <50 <50 <50
Ti <20 <20 <20 <20 <20
V <50 <50 <50 <50 Nd
Zn 1740 <5 5 160 590
nd = not determined
It is to be noted that the levels of copper (Cu),
iron (Fe) and zinc (Zn) were reduced after the treatment
with each of the metal adsorbing or absorbing materials.
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The reduction in the level of zinc was particularly
marked.
The levels of metals in the fuel may be reduced
further by optimisation of the conditions of the process,
or by passing the fuel through a second process of
contact with metal adsorbing or absorbing material, or by
alternative means. Further reductions in metal level may
be desirable to achieve the optimum reduction in the
formation of NOx and particulates during engine
operation.
The above data shows quite clearly that emissions of
NOx and particulates were reduced by clay treating Fuel
A. This was achieved without any essential effect on a
number of fuel properties (Table 1) or on emissions of
CO, total hydrocarbons and CO2 (Tables 7, 8 and 9).
Similar reductions in emissions of NOx and
particulates are to be expected when pre-treating the
hydrocarbon component(s) of the fuel with any metal
adsorbing or absorbing material, such as those described
above, particularly those which are effective in greatly
reducing the levels of zinc in the fuel.
Therefore, the present invention provides a means
for improving, i.e. reducing, emissions from a
compression-ignition engine which comprises pre-treating
with a metal adsorbing or absorbing material at least one
hydrocarbon component of a fuel to be used in such an
engine.
